An engine system generally comprises a turbocharger. A turbocharger typically includes a compressor that is rotationally coupled to a turbine via a shaft. Typically when a turbocharger is used with a combustion engine, the turbine of the turbocharger is disposed in the path of exhaust gas exiting the combustion engine. The turbine includes a wheel (hereinafter: ‘turbine wheel’) that is rotated by the flow of the exhaust gas. The turbine wheel is rotatably coupled to a wheel (hereinafter: ‘compressor wheel’) of a compressor, in the turbocharger. The compressor is disposed in-line with an air-intake system of the combustion engine. Rotation of the turbine by the exhaust gas flow causes the compressor wheel to likewise rotate, wherein rotation of the compressor wheel acts to increase the flow of fresh air into an air intake system. After directly rotating the turbine, and indirectly rotating the compressor, the exhaust gas exits the turbine.
The exhaust gas exiting the turbine contains nitrous oxides NOx, and hence emission of the exhaust gas into the environments would lead to emission of nitrous oxides NOx into the environment. The emissions of NOx from diesel and gasoline vehicles is regulated and/or restricted via legislation in many countries. A widely adopted route to reduce the NOx emissions is exhaust gas recirculation (EGR). The EGR may involve recirculating a controllable portion of the exhaust gas back into the air intake system. For example, in some internal combustion engines, a portion of exhaust gas generated by one or more combustion cylinders in the internal combustion engines is recirculated within the internal combustion engines via an EGR valve to mix the portion of the exhaust gas and an air-fuel mixture resulting in generation of air-fuel-exhaust mixture. Combustion cylinders in the internal combustion engines combust the air-fuel-exhaust mixture to generate energy and the exhaust gas.
Typically, an amount of exhaust gas to be recirculated into the combustion engine has direct and indirect impact on the performance of the engine and other emissions. Hence, there is a need of methods and systems that effectively control the EGR valve to achieve optimal engine performance along with meeting NOx emission restrictions.